Retractable drill bit and associated structures



Jan. 5, 1965 H. L. JOHNSON 3,164,215

RETRACTABLE DRILL, BIT AND ASSOCIATED STRUCTURES Filed April 26, 1961 United States Patent O 3,164,215 RETRACTABLE DRELL 3E1 AND ASSUQHATED STRUCTURES Howard L. Johnson, Los Angeles, Calif. (Box 5413, Inglewood, Calif.) Filed Apr. 26, 1961, Ser. No. 165,590 18 Claims. (Cl. 175-261) This invention relates to drill bits, particularly exemplified by the type which is used to drill oil and gas wells and for other deep earth boring. Such a bit, connected to the bottom of a tubular drill string which is progressively lengthened by addition of successive tubular segments to the top of the string, is moved against the bottom or face of the bore by rotation of the whole drill string from the surface. The descending bit must form a larger bore than the outside diameter of the drill string so that the latter may continue to sink within the deepening hcle without engaging the periphery of the bore. This annular space between the outer perimeter of the drill stern and the circumference of the bore is usually employed for the return circulation of fluid or drilling mud which is pumped down thru the tubular drill string and out at the bottom around the bit to cool and lubricate it, as well as to pick up chips and cuttings which it then carries to the surface thru the annular space. The gross solids are then filtered out and the fluid is recirculated in a continuing cycle, with more additives as required. Sometimes drilling is effected during reverse circulation of fluid, i.e. up the drill stem.

After some duration of drilling, a length of several miles of drill pipe may be standing in the hole, and when it becomes necessary from time to time to replace the bit on the bottom because it has worn down or broken, when using a conventional bit it is necessary to pull up this whole length of pipe, breaking it apart into segments as it emerges, in order to get the bit to the surface for detachment from the drill stem. Thus, as the well deepens, more time may eventually be spent in pulling the pipe than in actual drilling, particularly when in hard rock which may dull a fresh cutting edge in a few hours.

Most rotary drilling currently uses roller bits, typically three cones which individually turn by contact with the end face of the bore as the rotating drill stem (or its bottom bearing-mounts) press them thereagainst. In contrast, a preferred form of my present bit employs a nonrolling cutting face which sweeps the face of the bore in unison with the rotating drill string. There being no relative movement between the drill stem and the attached drill bit, no bearing mount is required between them. In addition, my bit can be mounted and dernounted on the bottom of the drill string while the latter remains in the bore, so that the bit may thus be replaced any number of times thru the tubular center of the drill string without pulling the pipe. At the same time, such retractable bit can form a bore larger than the inner perimeter of the drill string, or if desired, larger then the outer primeter of the drill string. In either case, the required diameter of the bore is maintained, and the rotating bit stabilized by reamers or side cutters carried by the drill stern; these latter are longer lasting than bottom rollers, particularly when not required to appreciably enlarge the bore.

My invention may be exemplified by an elongated bit which is longer but not as wide as the inner diameter of the ultimate segment of the drill stem so that (when vertically or longitudinally disposed) it can be moved lengthwise thru the hollow drill string, and by tilting or swinging thru a quarter turn (90) when adjacent the bottom, it is disposed in drilling position and coupled in frictional engagement with the tubular pipe for joint rotation in unison therewith, with (optionally) a lip of the now transversely 3,164,215 Patented Jan. 5, i965 mately to the inner diameter of the terminal segment of the drill stem.

The transversely disposed bit can carry conventional rolling cutters if desired, but preferably it is formed with a convex contact face or bore-engaging bottom having a spiral series of downward projecting, elongated teeth individually disposed at a sheer angle or bias to a theoretical spiral pattern emanating from the center of the drill stem (rather than from the center of the contact face). Such abrasive teeth may be inserted (e.g. diamond chips), overlaid (e.g. tungsten carbide) or cast on or with the bit as described in my pending application S.N. 823,548, Collapsible Drill Bit, filed June 29, 1959, now abandoned, of which this is a continuation-in-part.

Positioning of the bit on the bottom of the drill string (i.e. its shift from vertical or upright to horizontal or transverse position and concurrent anchoring in drilling position) is effected by cooperation with a transverse pivot rod, diametrically fixed across the open end of the terminal drill segment, so as to be engageahle by a transverse slot of the bit as it descends vertically or longitudinally within the tube. The pivot engagement slot of the bit need not be initially aligned rotationally at the time the bit is first introduced at the top of the drill string, but guide ways disposed about the inner face of the tube adjacent its distal end anterior to the pivot rod, automatically rotate the descending bit by edge contact therewith to a position from which its diametric open-bottom slot can drop down or move lengthwise along the tube until the fixed pivot rod is at the end of the bit slot, in which position the bit (then partially projecting from the bottom open-end of the drill string) swings about the rod a quarter turn or approximately to a fixed drilling position coupled for joint rotation with the drill string. During actual mounting and demounting of the bit on the bottom, the drill string is lifted and held elevated a short distance above the face of the bore by the drilling or operating apparatus at the surface; otherwise it stands on the transverse bit.

Supplementary to the pivot pin, other anchoring and aligning means are provided for interaction between the end of the drill string and the mounted bit, and in addition the upper face of the bit (when transversely disposed) is formed with downwardly constricted outlet walls which in conjunction with the adjacent, inner tubular face of the drill stem or attachment collar form funnel-like passages for channeling drilling fluid therethru to the bore face, so that by forced circulation or pumping of liquid or other fiuid down the drill pipe a force or pressure is continuously exerted on such channel walls to reinforce the drill bits seated position. Alternately, by temporarily reversing the direction of fluid flow (by the surface-located pumping unit) a force is available for uptilting the bit as the first step in its demounting from the pivot rod.

Although the drill bit can theoretically be mounted on the bottom of the drill stem simply by dropping it down from the top thru the column of liquid within the tube (so long as its engagement slot remains pointed downward) and raising the distal end of the standing drill stem olf the bottom; and similarly it could be withdrawn thru the tube simply by use of a magnet suspended by a cable from the surface, specially adapted means are also provided for conveying it up and down within the column. Thus a cylindrical carrier is suspended by an electric cable within the liquid column and carries an electric motor to move fluid thru the carrier and thus propel itself lengthwise in the column while holding the bit thereagainst with an electromagnet. By propulsion it can thus move the attached bit in either direction thru the liquid of the tube, quicker and more satisfactorily than it might be hauled up simply by cable or permitted to sink by its own weight thru the viscous column of drilling mud. In addition to the dependent bit being centered relative to with this attachment end up, in order to engage the pivot rod, the carrier keeps it thus even in tube sections where an unattached bit could tumble end over end.

Other objects and advantages will become apparent as the description proceeds, having reference to the presently preferred embodiment of the invention particularly illustrated in the accompanying drawing wherein FlGURE 1 is a side elevational view of the terminal segment or attachment collar of a rotary drill string carrying the reamers and with my retractable drill bit operatively mounted thereon and elevated somewhat from the a bottom of an earth bore, with the surface-located circulation elements indicated schematically;

FIGURES 2 and 3 are longitudinal sectional views of the lower end of the segment and mounted bit of P16- URE 1 at right angles to each other, without the side reamers and showing in side elevation the carrier disposed therein, with the position of the bit when attached upright to the carrier indicated in phantom line in FIGURE 2;

FIGURE 4 is a transverse sectional view thru the segment on the line 4-4 of FlGURE 3 showing the suspended carrier in top plan view therein;

FIGURE 5 is a transverse sectional View thru the segment on line 5--5 of FIGURE 2 showing the mounted drill bit in top plan view therein;

FIGURE 6 is a transverse sectional view thru the segment on line 66 of FIGURE 2, with the pivot rod and part of the mounted bit seen in top plan;

' FIGURE 7 is a bottom plan view of the bit alone, particularly showing the spiral arrangement of projecting teeth.

The invention is here illustrated in conjunction with the tubular, threadedly coupled, terminal segment or bit attachment-collar ill of a rotary drill string used in earth boring. For the present purpose, the open-bottomed se ment differs from other (anterior) tube segments by three structural features: (at) having a diametrically disposed, pivot rod 12 fixedly mounted adjacent its terminal annulus or fiat bottom 14 approximately flush therewith; (b) a diametrically opposing pair of identical, bit-aligning and anchoring spines 16, 18 longitudinally mounted along the inner face of said segment, perpendicular to the pivot rod 12 with their maximum periphery abutment ends 1'7, 19 disposed generally flush or spaced slightly above the annulus 14 (in the same transverse plane as the furthest edge of the pivot rod 12) and progressively diminishing in an upward taper, more-or-less elliptically curving to a blunt apex; (c) the ultimate band of the segment has its tubular wall thickened internally to provide along the upper edge thereof an identical pair of slide or guideways Z9, 22, each descending from a point 24, 25 (in longitudinal alignment with the corresponding spine 15, 18 beneath) rotationally a quarter turn to a longitudinal groove 23, fill which is immediately above and descending diametrically toward the parallel pivot rod 12, around each side of which it forms a bifurcate open end 29, 31 thru the inner perimeter of the annulus 14%. As will be shortly evident, the purpose of the identical pair of guideways is to rotate a descending bit by edge contact, either clockwise or counterclockwise, to a position wherein a diagonal slot in the bit is in line to drop over the pivot pin. The latter 12 then serves as a bit-mounting-axis about which swing the right and left lateral portions of the bit (as viewed in FIG. 2).

The drill bit 32 is formed with a dependent contact shoe 34 and with an upper body 35 formed integral therewith and partially separated therefrom by a transverse, open bottom (when disposed upright) slot 33 of a dimension to receive the length of the pivot rod 12 across the end of the slot and in such position the contact shoe 34 projecting partially from the open end of the collarto swing about the pivot rod a quarter turn or approximately to a transverse position wherein the convex cutting face 3;? of the shoe is entirely without the collar it The maximum transverse width (e, PEG. 6) of the fiat top or slide face 33 of the shoe is that of a chord of the inner perimeter of the collar slightly less than the length of the inner diameter, but the perpendicular length (f, FIG. '7) of the shoe (not the body) exceeds the inner tubular diameter so that the bit can only be disposed lengthwise therein, and when projected from the open end and rotated 90, a marginal lip ill extends beyond the outer perimeter of the drill stem with the arcuate bottom edge of the latter received in a corresponding groove 41 of the lip. The composite height (g, FIG. 2) of the bitwhich dimension is a second width when disposed uprightlikewise does not exceed the inner width e perpendicular thereto, and may be less. However, a transverse guide pin 42 exceeds such widths so that its opposite ends rest on the spirally descending slideways 2t 22 and drop into the down grooves 23, 3%, This locates the bit slot 38 parallel and in axial alignment (relative to the collar 10) with the pivot rod l2 immediately beneath, so that further longitudinal or down-movement of the bit causes the rod l2 to seat across the end of the slot.

By reason of its own weight distribution or built-in top-heaviness, the bit then tilts or swings about the rod 12 (aided, if necessary, by bumping the carrier 56 against it) until the projecting lip it? swings its groove ll up in abutment against the arcuate end 14 of the collar, and the opposite anchoring spine id is received in a correspondingly shaped depression 44 formed in the heel portion of the body 36. The diametrically projecting, contact ends of the cylindrical pin 42 have then swung thru one side or the other of the adjacent bifurcate channel 29, 31 to bring the pin 42 to rest in the same transverse plane as the pivot rod 12 in juxtaposition thereto (FIG. 2). It will be apparent that whether the contact ends of the pin 42 ride in the one side or the other of the bifurcate channel will depend upon which side of the pivot rod 12 the descending body nose 37 is disposed when the pin 42 contacts the spiral slideways 2d, 22. Since the upright drill bit could rotationally turn either to the right or left (ie. clockwise or counterclockwise), one anchoring spine is located on each side of the collar for locking abutment of the arcuately downswinging heel cavity 44 with either one as the case may be.

The bit body as on each side of the downwardly converging, aligning depressions 44, is formed with arcuate, downwardly restricted, channel walls 43, 45 (FIG. 5) which in conjunction with the adjacent, inner tubular wall of the collar in form downwardly constricted, outlet funnels 46, 47 for conveying descending fluid or drilling mud from within the drill string out to the bore face at a position (opposite the lip 40) from which loose cuttings and debris is best picked up and carried to the surface outside the drill stemor more specifically, to the shaker screen or filter 49 from whence the circulating means or pump 51 returns the fluids (with more additives if required) to the drill stem. The pressure of the fluid forced down the drill stem by the surface pump 5l-indeed even the Weight of this column of liquid standing on top of the transverse disposed drill bitacting against the constricting walls of the outlet funnels tends to hold the bit in its mounted or operative position, that is, with the upper groove 41 of the projecting lip portion seated firmly against an end segment of the collar annulus 14. Alternately, when demounting the bit, a reversal of the direction of fluid circulation (by the surface pump) will exert a suction or upending force upon the tunnel portion of the bit tending to swing it up or unseat it (the drill string being raised sufiiciently from the surface to enable it to tilt about the axis of the pivot rod 12).

For moving the upright drill bit lengthwise up and down within the tubular drill stem, there is provided a carrier 50 having a cylindrical body 52 formed with a peripheral series of (two or more) longitudinal fluid channels 54 open at both ends, and in internal electric motor 56 disposed for moving the fluid of the column thru the channels in either direction so as to propel the carrier thru the drill stem in the direction opposite its ejection. The outer perimeter of the body 52 is somewhat less than the inner perimeter of the terminal tube segment so as to be readily movable therealong, and it may also carry adjacent its outer face an annular series of outward extensible, telescoping tubes or arms 57 individually carrying a distal ball bearing 58 disposed for rolling or sliding contact with the inner wall of the drill ing tube segment 16. In addition, for guidance and relative centering of the carrier when passing thru tube segments of much greater diameter (nearer the surface or origin of the bore), there is provided an anterior series or circle of outwardly resilient or spring-urged guide arms 60 having outwardly convex, slide contact ends 61 which are thus adapted to pass over inward projecting shoulders or obstructions in the drill string from either direction.

Although self-propelled, the carrier 50 is suspended within the tube It) by a cable 62 carrying an electric conduit 64 from a surface generator (not shown) to supply current to the electric motor 56 as well as to a dependent electric magnet 66, the lower face of which carries a downward projecting, attachment stud 68. The curvature or walls of the stud 68, together with the bottom face of the electromagnet on each side thereof form a thrust engaging or attachment socket for the correspondingly shaped end of the upright disposed drill bit. The transverse stud 68 is thus shaped the same as the (identical) spines 16 and 18, and is centrally located to closely engage the depression 44-of the heel of the bit body and thus suspend the upright bit with its down-opening slot 38 vertically aligned with the pivot rod 12 even though not necessarily rotationally aligned therewith (FIG. 2), the latter being subsequently effected by the slideways 20, 22.

Desirably the drill stem carries, fairly close to the distal terminus, an outer circle or ring of contact-rotatable, side reamers 71 (FIG. 1) which serves the dual purpose of providing lateral support to the terminal segment or collar 10 of the drill string disposed upright in the bore so as to guard against lateral deviation or drift of the bore direction, as well as to insure a uniform or minimum diameter of the descending bore. Usually the reamers are not intended primarily to enlarge the bore from the diameter formed by the projecting lip 40, but the latter wears back radially (or occasionally breaks off) before it may be convenient to replace the bit, and in such event it can still continue to be used for a while as long as the reamers maintain the minimum diameter of the bore. As here illustrated, there are four pair of reamer mounts 70, 72 welded or otherwise secured to the outer tube face 10, the members of a pair being laterally staggered and each pair being separated equidistant about the tube segment 10. Each pair of mounts holds an angularly slanted (relative to the axis of the drill string), freely rotatable spindle 74 carrying a circle of elongated, generally parallel, cutting edges 76 individually disposed at a sheer contact angle with the side of the bore. Each roller 71 is in continuous contact with the bore wall for its entire length but each individual cutting edge 76 makes contact along only part of its length at any instant.

Although the center of the transverse length of the bit (FIG. '7) is eccentric to the center of the drill stem 10, the lowest point or nadir 80 is in line with the axis of rotation of the drill string and is the center of the theoretical spiral or pattern along which successive individual teeth 48 are located. For an equal radial distance on each side of this point (corresponding generally to the inner diameter of the drill stem), the contact face 35 of the bit is generally conic (h, FIG. 7), while the remaining outer area i also has a conic taper but may be more or less steep (i.e. based on a different cone) and of course extends out only on one side from the central conic plug it to overlie an arcuate edge 14 of the drill stem. In the aggregate, the series of teeth sweep the entire bottom face of the bore upon each rotation of the drill stern, but the cutting ability (or area concentration of teeth) of the conic plug may be greater than that of the radially extending lip, thus tending to maintain the undeviating direction of the bore. Accordingly, this outer area i of the cutting face 35 may be formed with more abrasive or effective teeth (such as diamond inserts) than the plug ortion h.

As indicated particularly in FIGURE 7, 'the bottom contact face 35 of the bit shoe may carry downward projecting, elongated, abrasive teeth 48 collectively arranged in a spiral pattern emanating from the theoretical center of the drill stem, and individually disposed at a sheer angle relative to the (rotary) direction of movement across the bore face, so that collectively they sweep the entire dished or concave face of the bore upon each rotation of the drill string, Alternately, however, as long as the cutting points or edges cumulatively wipe the whole area of the bore, they may be located without regard to such spiral pattern. In fabrication, the steel face of the shoe 34 may be overcast with any pattern of wear resistant, abrasive elevations such as cemented carbide, aluminum oxide ceramics, metallic borides, diamond chips or bortz, etc. or the entire bit and teeth may be cast of special alloy steel, replaceable on the teeth from time to time as worn away.

However the whole contact surface of the bit, and in particular the conic plug it may be formed of self abrasive material, that is (in contrast to just a knife edge of a severing or chipping tool), wherein the contact face of the bit is formed of abrasive material which as it is worn away by use, still continues to present an abrasive surface. Raised teeth of the same material may initially be formed on the abrasive surface as shown in FIGS. 4, 5 and 7. As described in my copending application, previously noted, desirably comminuted abrasive particles (cg. metallic carbide) are bonded to the steel alloy bit body by a matrix or mutual binder for metallic carbide and steel. In general, they are compositions which wet the carbon particles and are ferrous or other alloys having comparatively high concentrations of one or more of: nickel, cobalt, molybdenum, vanadium, titanium, tungsten; chromium, uranium, tantaliurn, colurnbium, chromium may be present in minor amounts. It should be noted that the melting point of the abrasive particles (e.g. 20 to 60 mesh) is considerably higher than that of either the binder or of the core alloy so that they substantially retain their shape and texture Within the molten alloy. In casting, when the abrasive particles are tungsten carbide, for example, they should not be heated (by contact with the molten alloy) above about 2400 F. for say 15 minutes, or not above 2700 F. or 3000 F. for a much shorter time. 7 I

As the pattern of cast teeth is worn away, the abrasive particles held in the matrix sheath continue to act as cutting points upon rotations of the bit, although with less uniform effectiveness than when they constituted a unitary pattern of teeth,

I claim:

1. A drill bit attachment-collar disposable as the terminal segment of a tubular, rotary drill stem, said collar having a transverse pivot rod centrally disposed across its lower end, a diametrically opposing pair of longitudinal bit-aligning spines located along the inner surface of said collar generally perpendicular to said rod, and a diametrically opposing pair of slideways disposed about the inner tubular surface above the pivot rod for rotationally aligning a longitudinally descending drill bit for thrust engagement with said pivot rod, whereby a drill bit formed with a transverse, rotary engaging surface disposablealongside said rod may swing approximately 98 about said rod between an upright, retractable position within said collar, and a transverse drilling position partially'suspended beneath said pivot rod and in frictional engagement with one of said aligning spines for joint rotation with said drill stem.

2. A drill bit attachment-collar disposable as the terminal segment of a tubular, rotary drill stem, said collar having internal contact means for rotating to alternate positions approximately 180 apart adjacent an end of said collar, a longitudinally descending drill bit, said collar also having more distal means for swinging such rotated bit approximately 90 transverse to its axis of descending rotation and projecting it at least partially from the distal end of said collar whereby said bit may be moved between a longitudinal, retractable position within said collar, and a transverse drilling position partially projecting therefrom, and anchoring means cooperative with such bit for selectively holding it in said transverse drilling position for joint rotation with said drill stem.

3. The attachment-collar of the preceding claim 2 wherein said internal rotational means comprise a diametrically opposing pair of spirally descending slideways disposed about the inner tubular surface of said attachment collar and spaced inward from the end thereof, each of said pair of slideways being curved a quarter turn in opposite directions, whereby a diametrically disposed cross pin carried by a descending drill bit may be rotated approximately 90 in either direction by sliding contact therewith so as to position the descending bit for subsequently swinging approximately 90 on a transverse axis to achieve an operating position across the end of said collar.

4. The combination comprising a drill bit attachmentcollar disposable as the terminal segment of a tubular, rotary drill stem, and a retractable drill bit characterized by a'length greater than the inner diameter of the collar and a width less than said diameter, said collar having internal rotational means for locating said bit at alternate positions approximately 180 apart adjacent an end of said collar, and other means for swinging such rotated bit approximately 90 transverse to its axis of rotation whereby the bit may be moved between a longitudinal, retractable position within the collar, and a transverse drilling position partially projecting therefrom, and anchoring means for selectively holding said bit in said transverse drilling position for joint rotation with said collar.

5. The combination of the preceding claim 4 wherein said anchoring means comprise a projecting edge of said .bit adapted in drilling position to frictionaliy underlie a segment end of said drill stem on one side-of the transverse axis for swinging the rotated bit, plus downwardly constricted fluid conduit means directed generally axial to the drill stem and located on the opposite side of said transverse axis from said projecting edge, whereby drilling fluid circulated downward within the drill stem and out thru said conduit means to the bore, maintains the mounted bit in drilling position on the-end of the rotary drill stem, and reversal of the direction of fluid circulation tends tounseat the bit.

6. The combination of the preceding claim 4 wherein said internal rotational means of the collar member and drill bit member comprise a diametrically opposing pair of spirally descending slideways disposed about one of said members, each of said pair of slideways being curved a quarter turn in opposite directions, whereby sliding contact with a diametrically disposed cross pin carried by 3 the other of said members serves to rotate a descending drill bit approximately in either direction so as to position the bit for subsequently swinging approximately 90 on a transverse axis to achieve an operating position across the end of said collar.

7. A drill bit adapted to be inserted and withdrawn through the tubular center of a rotary drill stem and to be operatively attached to the distal end thereof for rotation in unison therewith to form a bore of greater perimeter than the interior of the drill stem, said bit consisting essentially of a body portion of width and length each less than the inner diameter of such drill stem and a dependent, convex, contact shoe portion of only slightly less width and of greater length than said diameter, whereby said bit is movable longitudinally through said drill stem to and from the distal open end, adjacent which it is pivotally swingable thru approximately 90 upon a pivot rod diametrically disposed across said open end so as to be disposed transverse to said tubular stem with said contact shoe held outside the stem and with a radially projecting end lip of said shoe extending adjacent the outer perimeter of the drill stem, said bit having anchoring means cooperable with said drill stem and adapted selectively to hold it in such transverse operative position.

8. The drill bit of the preceding claim 7 wherein said shoe has an abrasive, convex contact face characterized by a series of elongated projecting teeth arranged in a generally converging spiral pattern relative to the center of the drill stem 9. The drill bit of the preceding claim 7 wherein said anchoring means include means responsive to fluid pressure exerted thru said tubular center against the mounted bit for holding it in operative position.

10. A rock bit adapted to be inserted and withdrawn thru the tubular center of an upstanding, rotary drill stem and to be operatively attached to the bottom thereof for rotation in unison therewith, said bit consisting essentially of a body portion of width and length each less than the inner diameter of said drill stern and a dependent contact shoe portion of no greater Width but of greater length than said diameter, said shoe being partially separated from said body by a slot formed transverse to the longitudinal axis of the shoe and adapted to receive therein a pivot rod centrally disposed across the bottom end of said drill stern and when thus engaged to be movable between an upright, retractable position and a transverse, operative position wherein said contact shoe is held outside said stem and overlying an edge thereof.

11. The rock bit of the preceding claim 10 wherein said contact shoe in operative position projects radially beyond said tubular edge so as to form a bore of greater perimeter than the exterior of the drill stem.

12. The rock bit of the preceding claim 10 wherein said body portion disposable within the drill stem opposite to the overlying portion of the contact shoe is formed with descending walls which in conjunction with the adjacent inner wall of the tubular stem forms a downwardly restricted outlet funnel disposed to convey liquid from the tubular stem to the bore face, the pressure of which flowing liquid thereagainst urges said bit to remain seated.

13. The rock bit of the preceding claim 10 wherein said shoe has a convex contact face characterized by a series of projecting abrasive teeth disposed collectively to sweep the face of an earth bore on each revolution of the drill stem.

14. The rock bit of the preceding claim 10 in combination with an upright, rotary, tubular drill stem having a pivot rod diametrically disposed across the bottom end thereof in position to be received in the transverse slot of said bit.

15. The rock bit of the preceding claim 10 wherein said body carries an opposing pair of generally diametrically projecting, guide pins, slidably cooperable with internal guide means of said drill stem for rotationally aligning the descending upright drill bit for thrust engagement of said slot with such pivot rod.

16. The rock bit of the preceding claim 15 in combination with an upright, rotary, tubular drill stern having a pivot rod diametrically disposed across the bottom end thereof in position to be received in the transverse slot of said bit when longitudinally aligned thereabove,

the inner face of the tubular drill stem proximate thereto being formed with an opposing, similar pair of contact slideways disposed to progressively rotate the descending rock bit by contact with said projecting guide pins either clockwise or counterclockwise to a position of mutual alignment of the pivot rod and engaging slot.

17. A rock bit adapted to be operatively disposed partly within and partly projecting from the distal end of a tubular rotary drill stem with a radially extending lip overlying an arcuate edge of said drill stem, said bit being adapted upon rotation by and in unison with the drill stem to form a bore of greater perimeter than the interior of the drill stern, said bit having a self-abrasive, radially convex, contact face characterized bya dependent conic portion of diameter approximatingthe interior of said drill stern and coaxial therewith, and having a spiral pattern of projecting cutting teeth disposed over the contact areas of both the conic portion and of said lip.

18. In combination with a tubular rotary drill stern having associated means 'for circulating drilling fluid down the interior of said stem to a bore face and back to the operating head by passage within the bore along the exterior of the drill stem, said means also beingadapted selectively to reverse such direction of circulation within the drill stern and bore, a drill bit operatively mounted on the far end of the drill stern by pivot means forming a transverse bit-mounting-axis which thus delineates lateral bit portions on opposite sides thereof, whereby the portions of the bit may be swung about said axisbetween a longitudinal retractable position within the drill stem and a transverse drilling position having one lateral portion partially frictionally underlying an end segment of said drill stern, said bit being further characterized by downwardly constricted, funnel-shaped channel means in said opposite lateral portion adapted to convey circulating drilling fluid from the interior of the drill stem to the bore face and thus to urge the transversely disposed bit seated in operative position by down pressure of fluid therethru and alternately to urge the bit to swing about said bit-mounting-axis toward longitudinal retracted position upon reversal of such fluid flow.

References Cited in the file of this patent UNlTED STATES PATENTS 487,989 Chapman Dec. 13, 1892 1,295,969 Carmichael Mar. 4, 1919 1,454,984 Stewart May 15, 1923 1,819,798 Stokes Aug. 18, 1931 1,996,132 Walker Apr. 2,1935 2,277,989 Kinnear Mar. 31, 1942 2,371,489 Williams Mar. 13, 1945 2,654,627 Story 'Oct 6, 1953 2,660,468 Cook Nov. 24, 1953 

4. THE COMBINATION COMPRISING A DRILL BIT ATTACHMENTCOLLAR DISPOSABLE AS THE TERMINAL SEGMENT OF A TUBULAR, ROTARY DRILL STEM, AND A RETRACTABLE DRILL BIT CHARACTERIZED BY A LENGTH GREATER THAN THE INNER DIAMETER OF THE COLLAR AND A WIDTH LESS THAN SAID DIAMETER, SAID COLLAR HAVING INTERNAL ROTATIONAL MEANS FOR LOCATING SAID BIT AT ALTERNATE POSITIONS APPROXIMATELY 180* APART ADJACENT AN END OF SAID COLLAR, AND OTHER MEANS FOR SWINGING SUCH ROTATED BIT APPROXIMATELY 90* TRANSVERSE TO ITS AXIS OF ROTATION WHEREBY THE BIT MAY BE MOVED BETWEEN A LONGITUDINAL, RETRACTABLE POSITION WITHIN THE COLLAR, AND A TRANSVERSE DRILLING POSITION PARTIALLY PROJECTING THEREFROM, AND ANCHORING MEANS FOR SELECTIVELY HOLDING SAID BIT IN SAID TRANSVERSE DRILLING POSITION FOR JOINT ROTATION WITH SAID COLLAR. 